1. Field of the Invention
This invention relates to a method for connecting semiconductor material, and more particularly to a connecting method applied when a wireless bonding method, in particular a flip chip bonding method or a tape carrier bonding method are applied for bonding semiconductor tips to a substrate, such as a connection material to be used in the connection method and semiconductor devices manufactured by the above-mentioned connection method.
2. Description of the Prior Art
As the conventional system for forming a bump electrode by using a wire bonding machine, two Japanese publications are relevant; they are Japanese Patent Publication Nos. 61-43438 and 61-219159. In the prior art, after the bump electrode is bonded, the desired position of the wire is cut by an electrical discharge with an electric torch in order to make a specified size of the wire remaining in the ball.
The above-mentioned prior art involves a complicated processing step and has decreased work efficiency.
Other connecting methods are disclosed in Japanese Patent Publication No. 59-208751, wherein the wire is clamped with a clamper after the bonding operation and cut while being pulled up, i.e., a connecting method requiring no special cutting method is disclosed. However, as described in this publication, although a mere clamping and pulling up of the wire with a clamper enables the wire to be cut, it is impossible to keep the size of the wire remaining in the ball always constant, to perform a continuous stable bonding operation and to provide a semiconductor device having high reliability.
At present, as a bump electrode material, PbSn of 5 wt %, PbSn of 40 wt % or the like is used. However, it has been found that a connection of alloy wire made by drawing the alloy manufactured by a normal casting method through a die using a wire bonder operation requires frequent cutting of the wire not at the root part of the ball but at a midway part of the wire. This causes substantial variation in its length and as such the wire is not suitable as a bump electrode.
Cutting of the alloy wire at the wire part is caused by the fact that a tensile strength of the root part of the ball is not sufficiently low as compared with a tensile strength of the wire part.
Due to this reason, the conventional method described in Japanese Patent Publication No. 59-208751 can not always keep the size of wire remaining in the ball constant.